ᐅ Using OSB as Bathroom Flooring – How to Waterproof It?

Hello,

We are currently renovating our house from 1955, including the bathroom. Since we can only allow a maximum floor buildup of 2cm (0.8 inches), we have recessed 22mm (7/8 inch) OSB flush between the floor joists. On top of that, another 12mm (1/2 inch) OSB layer will be installed and screwed down.

We are now looking for a suitable waterproofing solution for this setup.

We understand that OSB is far from ideal for bathroom floors, but an alternative construction would have resulted in a significant step into the bathroom.

We plan to install glued vinyl flooring.

Who can offer tips and advice? There must be solutions for this, as OSB is, for example, widely used in the USA for similar purposes.

Best regards and thank you

We have that too. The tiler normally sealed it with the blue stuff. It has been absolutely stable and effective for 6 years.

Waterproof membrane. As used in other bathrooms as well. Brands like Sopro, Knauf, Isolbau, etc. It is glued onto the floor (also in the shower). Please do not use liquid waterproofing. Also, extend it a few centimeters (inches) up over the corners and wall connections.

My brother, during his last bathroom renovation, completely covered the wooden floor (including the edges) with thick bitumen sheets (applied hot). Naturally, he also applied the usual waterproof coatings on top of that (under the tiles).